1. Field of the Invention
The present invention relates to a saw blade, and in particular to a saw blade such as a bandsaw blade, a circular saw blade, and a hacksaw blade.
2. Description of the Prior Art
Conventionally, a metal cutting machine such as a bandsaw machine is used to cut a metallic workpiece. The bandsaw blade used by such a bandsaw machine is usually set in a pattern such as a raker set, wave set, or straight set pattern, and the like, in order to minimize vibration and noise, and, in addition, each tooth is set to an unequal pitch. Furthermore, bandsaw blades in which the height of each tooth is different have been developed for sawing difficult-to-cut materials such as stainless steel.
In conventional bandsaw blades, it is the usual practice, after each of the teeth have been formed at a uniform height, to set the pattern by combining teeth set in a slight bend in the direction of the thickness of the bandsaw blade (the transverse direction) with unset teeth which are not bent in the transverse direction.
When a workpiece is being sawn by a bandsaw blade, chips are produced which are almost the same thickness as the thickness of the backing of the bandsaw blade. This makes it very difficult to discharge these chips to the outside from the space between the groove formed by the sawing action in the workpiece and the backing of the bandsaw blade. Specifically, the chips have a tendency to collect in the gullet formed between the teeth of a conventional bandsaw blade. Once this gullet is filled with chips, these chips cause the bandsaw blade to be elevated in the feed direction of the cut relative to the workpiece. In proportion to the amount by which the bandsaw blade is elevated, it produces a course deviation to the right or left relative to its direction of travel. Accordingly, in conventional bandsaw blades the problem is produced by which the cut veers to the direction of the deviation.
In addition, in conventional bandsaw blades, when the blade continues to cut the workpiece after chips have collected in the gullet, the chips are compressed so that the problem arises whereby the pressure of the chips cause breakage of the saw teeth.
In conventional bandsaw blades, although there are slight differences in height between the tips of the unset teeth and the tips of the opposedly set teeth, for example, when taken from the locus of the center of the thick portion of the unset teeth, the tips of each tooth are almost the same height. Therefore, when the workpiece is being cut, the unset teeth are not always the first teeth to cut into the workpiece. The oppositely set teeth can also be the first to cut into the workpiece. For example, when the left-set teeth are the first to cut into the workpiece, the cutting resistance causes the bandsaw to have the inclination to swing to the right side. Specifically, there is the problem in a conventional bandsaw that vibration and deviation of the cut in the transverse direction is easily produced.
When stainless steel, which is a difficult-to-cut material, is being cut by a conventional bandsaw, the feeding force of each tooth is small. If the bandsaw blade cannot cut the workpiece, the tips of the bandsaw blade teeth will rub against the surface of the workpiece so that a work-hardened layer is formed on the surface, making the hard-to-cut material even more difficult to cut. Specifically, with conventional bandsaw blades, it is very difficult to provide one bandsaw blade which is capable of cutting all materials from easy-to-cut materials to hard-to-cut materials.
Conventionally, in a bandsaw blade developed for cutting difficult-to-cut materials, the teeth are made to have varying height in order to increase the feeding force of specific teeth. In a bandsaw blade for cutting difficult-to-cut materials, the longer or larger teeth only carry out the cutting of the workpiece, and the shorter or smaller teeth are usually not used. Accordingly, in this type of bandsaw blade the long teeth carry the major share of the load, and along with the problem of severe abrasion, the bandsaw blade which was cutting the workpiece is bent into the form of an arc. In the instant that it finishes cutting the workpiece, the disappearance of the resistance in the direction of the cut causes it to immediately revert to a straight line. Accordingly, if a small mass of material, which has not been cut, remains in the form of small protruding sections (burrs), then the short teeth, which for all practical purposes carried no load, strike the burrs so that the teeth are easily fractured.
In addition, in a bandsaw blade with teeth of different lengths, there is the problem that the inside corners of the tips of short teeth which are oppositely set, specifically the left corner of right-set teeth, and the right corner of left-set teeth looking from the direction of the cut, are obstructed by the long teeth and do no cutting whatever.
Also, in a sawblade with differing teeth heights it is usual to continuously join the short right-set teeth and left-set teeth. For this reason, there is also the problem that the long teeth which are positioned in the direction of the cut next to the oppositely set short teeth receive an especially large load.
In today's advanced technology, machine tools are required to be of high precision and high efficiency. In a bandsaw machine the precision of the cut is a big problem.
Specifically, there is a direct relationship between the bandsaw blade used and the accuracy of the cut of a bandsaw machine. In forming the configuration of the tips of the teeth of the bandsaw blades, it is usual to set the pattern in the direction of the thickness of the bandsaw blade (the transverse direction) by combining the bent, oppositely set teeth and the unset teeth which are not oppositely bent.
For example, a raker set pattern is formed from three kinds of teeth in one group (set) that is, a right-set tooth with the bend carried out in the right direction, a left-set tooth with the bend carried out in the left direction joined as a pair, and a unset tooth which is not bent in the left or right directions. It is usual that in the order in the direction of the advance of the blade, directly in front of the one unset tooth there is always a right-set tooth or, in the other case, a left-set tooth, prescribed in the same direction.
For example, when the cutting order of the teeth in a raker set is a right-set tooth, followed by a left-set tooth, then an unset tooth, the tooth before the unset tooth is always a left-set tooth, and a right-set tooth precedes a left-set tooth. Here, if taking the unset tooth as the base in the running direction of the saw blade, the distance from the unset tooth to the left-set tooth is one pitch and the distance from the unset tooth to the right set tooth is two pitches. Accordingly, because the saw blade descends at a fixed velocity during the sawing of the workpiece, the feeding amount into the workpiece is larger when the pitch is larger, and the load is also larger. Specifically, the left corner of the unset tooth cuts the portion remaining from the cut by the left-set tooth, and the right corner of the unset tooth cuts the portion remaining from the cut by the right-set tooth. Accordingly, the right corner of the unset tooth bears a greater load than the left corner, and the abrasion of the right corner of the unset tooth is greater than the abrasion of the left corner. This then gives rise to the problem of abrasion occurring on one side of the unset tooth so that a cut deviation is easily produced.
This problem not only occurs with the raker set, but is produced in all saw blades in which the configuration is always a right-set tooth or a left-set tooth immediately before one unset tooth.
At the present time, in the same way that a special bandsaw blade must be used for difficult-to-cut materials, it is necessary to classify bandsaw blades to be used depending on the material to be cut specifically for easy-to-cut materials, for large diameter materials, for small diameter materials etc.